Electro-optical element and method for manufacturing thereof, optical module and method for driving thereof

ABSTRACT

An electro-optical element is provided including a light-emitting element part and a light-receiving element part, wherein an optical thickness d of the light-receiving element part satisfies the following condition:
 
 d=mλ/2 
where λ is a design wavelength of the light-emitting element part, and m is a natural number greater than or equal to one.

This is a Division of application Ser. No. 10/892,372, filed Jul. 16,2004, which in turn claims the benefit of Japanese Application No.2003-278177, filed Jul. 23, 2003. The entire disclosure of the priorapplication is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to an electro-optical element and a methodfor manufacturing an electro-optical element, an optical module and amethod to drive an optical module.

2. Description of Related Art

A related art light-emitting element, for example, a surface emittingsemiconductor laser is disclosed in Japanese Unexamined PatentPublication Application No. 10-135568. Generally, if a light-emittingelement is used for optical communication, optical arithmetic or a lightsource for various kinds of sensors, an optical characteristic of anemitted light, for example a radiation angle or a wavelength of light,requires control.

In the above related art light-emitting element, a light-detecting partis stacked on the light-emitting element. This light-detecting partreceives a part of the light emitted from the light-emitting element,thereby detecting its light volume. Therefore, a diameter of thelight-detecting part is made smaller than that of a light-emittingregion of the light-emitting element so that part of the light emittedfrom the light-emitting element can be introduced into thelight-detecting part.

In the above related art light-emitting element, the light-detectingpart can be used as a normal light-receiving element, instead of or inaddition to, its usage to monitor the power of light generated in thelight-emitting element. In this case, as mentioned above, the diameterof the light-detecting part is generally made smaller than that of thelight-emitting region of the light-emitting element part. However, thisresults in the light receiving area of the light-detecting part beingtoo small thereby causing insufficient sensitivity.

SUMMARY OF THE INVENTION

An exemplary aspect of the invention provides an electro-optical elementincluding a light-emitting element part and a light-receiving elementpart, and a method for manufacturing an electro-optical element.

Also, an exemplary aspect of the invention provides an optical moduleincluding an electro-optical element of an exemplary aspect of theinvention and a method to drive the electro-optical element and anoptical transmitting device including the electro-optical element.

Electro-Optical Element

An electro-optical element of an exemplary aspect of the inventionincludes a light-emitting element part, a light-receiving element partthat includes an optical surface and is provided on the light-emittingelement part, and an optical member provided at least on the opticalsurface. The electro-optical element emits light at least in a directionthat the light-emitting element part and the light-receiving elementpart are formed in layers.

Here, the “optical member” refers to a member having a function ofchanging an optical characteristic or traveling direction of light. Asfor the “optical characteristic”, for example, a wavelength, adeflection, a radiation angle or the like are exemplified. An opticalmember can be, for example, a lens or a deflection element.

Also, the “optical surface” refers to a surface that light passesthrough. The “optical surface” may be an exiting surface of lighttraveling from the electro-optical element of an exemplary aspect of theinvention to an outside or an incident surface of the light travelingfrom the outside to the electro-optical element of an exemplary aspectof the invention. The “outside” refers to a region excluding theelectro-optical element of the invention.

According to the electro-optical element of an exemplary aspect of theinvention, the electro-optical element including the optical memberwhose placement position, shape, and size are properly controlled can beachieved.

Applications of the above-mentioned electro-optical element may includefollowing exemplary aspects (1) through (8).

(1) An upper surface of the light-receiving element part may include theoptical surface.

(2) A cross-sectional surface cut by a plane being parallel to theoptical surface of the optical member may be at least one of a circleand an oval.

In this case, the optical surface is at least one of the circle and theoval and a longest diameter of the cross-sectional surface of theoptical member may be larger than the longest diameter of thecross-sectional surface of the optical surface. Here, if the opticalsurface is the circle, the longest diameter is a diameter. If theoptical surface is the oval, the longest diameter is a long axis. Thisis applied to the optical member in same manner.

(3) The optical member may be formed by curing a liquid member byapplying an energy.

(4) The light-receiving element part may include a function ofconverting a part of the light emitted from the light-emitting elementpart to a current.

(5) The light-receiving element part may include a function ofconverting a part of the light emitted from the light-emitting elementpart to a current.

In this case, an optical thickness d of the light-receiving element partmay be represented by the following formula (1).d=mλ/2 (m is a natural number greater than or equal to one)  Formula (1)where a design wavelength of the light-emitting element part is λ.

Here, the “design wavelength” refers to a wavelength of the light whoseintensity is the maximum among the light generated in the light-emittingelement part. Also, the “optical thickness” refers to the value that iscalculated by multiplying an actual film thickness of the layer by arefractive index.

(6) The light-emitting element part may include a first mirror, anactive layer provided on the first mirror, and a second mirror providedon the active layer. The light-receiving element part may include afirst contact layer, a light absorption layer provided on the firstcontact layer, and a second contact layer provided on the lightabsorption layer.

(7) The light-emitting element part may function as a surface emittingsemiconductor laser.

(8) The optical member may function as a lens.

Method to Manufacture an Electro-Optical Element

An exemplary method to manufacture an electro-optical element of anexemplary aspect of the invention includes forming a stacked body madeup of a light-emitting element part and a light-receiving element partincluding an optical surface; forming an optical member precursor byejecting a liquid drop to the optical surface; and forming an opticalmember by curing the optical member precursor.

According to a method to manufacture an electro-optical element of anexemplary aspect of the invention, the electro-optical element includingthe optical member whose placement position, shape, and size areproperly controlled can be achieved.

The liquid drop may be made of a liquid member that is cured by applyingenergy.

Optical Module and an Optical Transmitting Device

An optical module of an exemplary aspect of the invention includes afirst electro-optical element, a second electro-optical element and anoptical waveguide. The first and second electro-optical elements are theelectro-optical element described above. A light emitted from theoptical surface of the first element transmits through the opticalwaveguide, thereby being incident on the optical surface of the secondelement. A light emitted from the optical surface of the second elementtransmits through the optical waveguide, thereby being incident on theoptical surface of the first element.

An optical transmitting device according to an aspect of the inventionincludes the above-mentioned optical module.

Method to Drive an Optical Module

A method to drive an optical module of an exemplary aspect of theinvention is a method to drive the optical module including a firstelectro-optical element, a second electro-optical element, and anoptical waveguide. Here, the first electro-optical element and secondelectro-optical element are the above-mentioned electro-optical element.The method includes controlling the first and the second electro-opticalelement such that if the first electro-optical element is in alight-emitting state, the second electro-optical element is in alight-receiving state, and if the first electro-optical element is inthe light-receiving state, the second electro-optical element is in thelight-emitting state.

In an exemplary aspect of the present invention, the “light-receivingstate” refers to a state where a light-receiving function is capable ofbeing demonstrated. This does not concern whether the electro-opticalelement of an exemplary aspect of the invention actually receives thelight or not.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustrating an electro-optical element of a firstexemplary embodiment of the invention;

FIG. 2 is a schematic illustrating the electro-optical element shown inFIG. 1;

FIG. 3 is a schematic illustrating a manufacturing process of theelectro-optical element shown in FIG. 1;

FIG. 4 is a schematic illustrating a manufacturing process of theelectro-optical element shown in FIG. 1;

FIG. 5 is a schematic illustrating a manufacturing process of theelectro-optical element shown in FIG. 1;

FIG. 6 is a schematic illustrating a manufacturing process of theelectro-optical element shown in FIG. 1;

FIG. 7 is a schematic illustrating a manufacturing process of theelectro-optical element shown in FIG. 1;

FIG. 8 is a schematic illustrating a manufacturing process of theelectro-optical element shown in FIG. 1;

FIG. 9 is a schematic illustrating a manufacturing process of theelectro-optical element shown in FIG. 1;

FIG. 10 is a schematic illustrating a manufacturing process of theelectro-optical element shown in FIG. 1;

FIG. 11 is a schematic illustrating an electro-optical element of asecond exemplary embodiment of the invention;

FIG. 12 is a schematic illustrating an electro-optical element of athird exemplary embodiment of the invention;

FIG. 13 is a schematic illustrating the electro-optical element shown inFIG. 12;

FIG. 14 is a schematic illustrating a first reflecting rate and a secondreflecting rate of the electro-optical element shown in FIG. 12 with thecondition that a design wavelength is 850 nm;

FIG. 15 is a schematic illustrating an optical module according to afourth exemplary embodiment of the invention;

FIG. 16 is a schematic illustrating an example of a drive circuit for anelectro-optical element shown in FIG. 15;

FIG. 17 is a schematic illustrating an optical transmitting deviceaccording to a fifth exemplary embodiment of the invention; and

FIG. 18 is a schematic illustrating a usage of a optical transmittingdevice according to a sixth exemplary embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the invention will now be described withreference to the accompanying drawings.

First Exemplary Embodiment

1. Construction of an Electro-Optical Element

FIG. 1 is a schematic illustrating an electro-optical element 100according to a first exemplary embodiment of the invention. FIG. 2 is aschematic illustrating the electro-optical element 100 in FIG. 1.

The electro-optical element 100 in the exemplary embodiment, as shown inFIG. 1, includes a light-emitting element part 140 and a light-receivingelement part 120. In the exemplary embodiment, a case where thelight-emitting element part 140 functions as a surface emittingsemiconductor laser and the light-receiving element part 120 functionsas a light-detecting part is described.

In this electro-optical element 100, a laser light can be emitted froman optical surface 108 in a direction that the light-emitting elementpart 140 and the light-receiving element part 120 are formed in layers.An optical member 160 is disposed at least on the optical surface 108.The light-emitting element part 140, the light-receiving element part120, and other elements will be described below.

Light Emitting Element Part

The light-emitting element part 140 is formed on a semiconductorsubstrate 101 (in this exemplary embodiment, a n-type GaAs (GalliumArsenide) substrate). The light-emitting element part 140 constructs avertical resonator (hereafter, resonator).

Also, the light-emitting element part 140 may include a semiconductorstack body 130 of columnar like shape (hereafter, columnar part).

The light-emitting element part 140 is constructed by forming, forexample, a distributed reflection type multilayer film mirror 102(hereafter, a first mirror) including 40 pairs of a n-typeAl_(0.9)Ga_(0.1)As (aluminum-gallium-arsenide) layer and a n-typeAl_(0.15)Ga_(0.85)As layer alternately deposited one above another, anactive layer 103 including a Al_(0.3)Ga_(0.7)As barrier layer and a GaAswell layer that includes a quantum well structure constructing threelayers, and a distributed reflection type multilayer film mirror 104(hereafter, a second mirror) including 29.5 pairs of a p-typeAl_(0.9)G_(0.1)As layer and a p-type Al_(0.15)Ga_(0.85)As layeralternately deposited one above another in this order. A composition ofeach layer and the number of layers in the first mirror 102, the activelayer 103, and the second mirror 104 are not limited to those describedabove.

The second mirror 104 is p-type doped by carbon (C), for example. Thefirst mirror 102 is n-type doped by silicon (Si), for example.Therefore, a pin diode is formed by the p-type second mirror 104, theactive layer in which no impurities is doped, and n-type first mirror102.

In the light-emitting element part 140, the columnar part 130 is formedon the first mirror 102 by etching, in a circular shape viewed from anupper surface 104 a of the second mirror 104. The columnar part 130includes the second mirror 104, the active layer 103 and a part of thefirst mirror 102. In the exemplary embodiment, while a plan shape of thecolumnar part 130 is described as the circular shape, any shape can beacceptable for the shape.

A current constriction layer 105 made of aluminum oxide is formed in aregion that is closer to the active layer 103 among the layersconstructing the second mirror 104. The current constriction layer 105is formed in substantially a ring. Accordingly, the current constrictionlayer 105 shows a concentric circle as in a cross-sectional surface cutby a plane being parallel to a surface 101 a of the semiconductorsubstrate 101 in FIG. 1.

Also, a first electrode 107 and a second electrode 109 are formed in thelight-emitting element part 140.

The first electrode 107 and the second electrode 109 are used to drivethe light-emitting element part 140. The second electrode 109 is formedon an upper surface 140 a of the light-emitting element part 140.Specifically, as shown in FIG. 2, the first electrode 107 and the secondelectrode 109 have substantially a plan shape of a ring. The firstelectrode 107 is formed so as to surround the columnar part 130 and thesecond electrode 109 is formed so as to surround the light-receivingelement part 120. The columnar part 130 is formed inside the firstelectrode 107 and the light-receiving element part 120 is formed insidethe second electrode 109.

In the exemplary embodiment, while the case where the first electrode107 is formed on the first mirror 102 has been described, the firstelectrode 107 may be formed on a backside 101 b of the semiconductorsubstrate 101.

The above may be applied to a second and a third exemplary embodimentdescribed later in same manner.

The first electrode 107 is made up of stacked layers of gold (Au) and analloy of Au and germanium (Ge), for example. The second electrode 109 ismade up of stacked layers of platinum (Pt), titanium (Ti), and Au. Acurrent is injected in the active layer 103 by the first electrode 107and the second electrode 109. A material forming the first electrode 107and the second electrode 109 is not limited as described above. Forexample, an alloy of Au and zinc (Zn) are applicable.

Light Receiving Element Part

The light-receiving element part 120 is formed on the light-emittingelement part 140 and includes the optical surface 108. As for theelectro-optical element 100 in the exemplary embodiment, an uppersurface of the light-receiving element part 120 includes the opticalsurface 108. At least upper part of the light-receiving element part 120is a columnar like shape.

Also, the light-receiving element part 120 includes a first contactlayer 111, a light absorption layer 112, and a second contact layer 113.The first contact layer 111 is formed on the second mirror 104 of thelight-emitting element part 140. The light absorption layer 112 isformed on the first contact layer 111. The second contact layer 113 isformed on the light absorption layer 112. In addition, as for thelight-receiving element part 120 in the exemplary embodiment, a casewhere a plan shape of the first contact layer 111 is larger than that ofthe light absorption layer 112 and that of the second contact layer 113is shown (refer to FIG. 1 and FIG. 2). Also, the first contact layer 111contacts the second electrode 109 and a third electrode 116. A part ofthe third electrode 116 is formed on the second electrode 109.Therefore, a side surface of the first contact layer 111 contacts thesecond electrode 119 and an upper surface of the second electrode 119contacts the third electrode 116.

The first contact layer 111 can be formed by the n-type GaAs layer, forexample. The light absorption layer 112 can be formed by the GaAs layerin which an impurity is not introduced, for example. The second contactlayer 113 can be formed by the p-type GaAs layer. Specifically, thefirst contact layer 111 is p-type doped by C, for example. The secondcontact layer 113 is n-type doped by Si, for example. Therefore, the pindiode is formed by the n-type first contact layer 111, the lightabsorption layer 112 in which no impurities are doped, and p-type thesecond contact layer 113.

The third electrode 116 and a fourth electrode 110 are formed in thelight-receiving element part 120. The third electrode 116 and the fourthelectrode 110 are used to drive the light-receiving element part 120.Also, as for the electro-optical element 100 in the exemplaryembodiment, the same material as that of the first electrode 107 canform the third electrode 116. The same material as that of the secondelectrode 109 can form the fourth electrode 110.

The fourth electrode 110 is formed on an upper surface of thelight-receiving element part 120 (on the second contact layer 113). Anopening 114 is provided in the fourth electrode 110. A bottom of theopening 114 is the optical surface 108. Therefore, changing a plan shapeand size of the opening 114 can set a shape and size of the opticalsurface 108. In the exemplary embodiment, as shown in FIG. 1, theoptical surface 108 is shown in substantially a circle shape as anexample.

Optical Member

As for the electro-optical element 100 in the exemplary embodiment, theoptical member 160 is disposed at least on the optical surface 108.Specifically, as shown in FIG. 1, the optical member 160 is disposed onthe upper surface of the light-receiving element part 120. In theexemplary embodiment, a case where the electro-optical element 160functions as a lens will be described. In this case, the light generatedin the light-emitting element part 140 emits from the optical surface108 and is condensed by the optical member 160 so as to emit to theoutside.

The optical member 160 is formed by curing a liquid material (forexample, a precursor of an ultraviolet curable resin or a thermosettingresin) that is capable of curing by an energy, for example, such as heator light or the like. Examples of the ultraviolet curable resin includean acrylic-type ultraviolet curable resin and epoxy- type resin. Also,for the thermosetting resin, a thermosetting polyimide-type resin or thelike are exemplified.

The precursor of the ultraviolet curable resin is cured by anirradiation of ultraviolet light in a short time. Thus, this makes itpossible to cure without passing through a process, such as heating inwhich the light-emitting element and light-receiving element are easilydamaged. Consequently, forming the optical member 160 by employing theprecursor of the ultraviolet curable resin, any influence on the elementcan be lessened.

Specifically, the optical member 160 is disposed as follows (refer toFIG. 9 and FIG. 10): A liquid drop 160 a made of the liquid material isejected at least to the optical surface 108 (in the exemplaryembodiment, on the top of the light-receiving element part 120) so as toform a precursor of the optical member 160 b. Then, the precursor of theoptical member 160 b is cured. A method to form the optical member 160will be described later.

Also, the optical member 160 is a cutting sphere like. Since the opticalmember 160 is a cutting sphere like, the optical member 160 can be usedas a lens or a deflection element. For example, by forming the uppersurface of the light-receiving element part 120 a circle, insubstantially a three dimensional shape of the optical member 160 can beformed the cutting sphere like. Alternatively, shaping the upper surfaceof the light-receiving element part 120 an oval, a three dimensionalshape of the optical member 160 can be formed the cutting oval bodylike.

Here, the “cutting sphere ” means a shape obtained by cutting a spherewith a plane. This sphere includes not only a perfect sphere but also ashape similar to the sphere.

As for the electro-optical element 100 in this exemplary embodiment, across-sectional surface that is obtained by cutting the optical member160 with a plane being parallel to the optical surface 108 is a circleand the optical surface 108 is shaped a circle. In this case, as shownin FIG. 1 and FIG. 2, it enables the longest diameter r1 (a diameter) ofthe cross-sectional surface that is obtained by cutting the opticalmember 160 with a plane parallel to the optical surface 108 to be largerthan the longest diameter (a diameter) r2 of the upper surface of thelight-receiving element part 120 and the longest diameter (a diameter)r3 of the optical surface 108, because at least the upper part of thelight-receiving element part 120 has a columnar like shape.

Whole Construction

As for the electro-optical element 100 in this exemplary embodiment, anpnp construction is formed, as a whole, by the n-type first mirror 102and the p-type second mirror of the light-emitting element part 140, andthe n-type first contact layer 111 and the p-type second contact layer113 of the light-receiving element part 120. By interchanging the p-typeand n-type in the each layer described above, a pnpn construction can beformed as a whole. Alternatively, although not shown in the FIGS., byinterchanging p-type and n-type of the each layer in either thelight-emitting element part 140 or the light-receiving element part 120,the light-emitting element part 140 and the light-receiving element part120 can be formed as the npn or pnp construction as a whole. The abovemay be applied to the second and third exemplary embodiment describedbelow.

The light-receiving element part 120 has a function of monitoring anoutput of light generated in the light-emitting element part 140.

Specifically, the light-receiving element part 120 converts the lightgenerated in the light-emitting element part 140 to a current. Theoutput of the light generated in the light-emitting element part 140 isdetected by a value of the current.

Specifically, in the light-receiving element part 120, a part of thelight generated in the light-transmitting element part 140 is absorbedin the light absorption layer 112. The absorbed light causes a lightexcitation in the light absorption layer 112, thereby producing anelectron and a positive hole. By an electric field applied from outsideof the element, the electron is moved to the third electrode 116, andthe positive hole is moved to the fourth electrode respectively. As aresult, a current arises, in a direction from the first contact layer111 to the second contact layer 113.

Also, principally a bias voltage applied to the light-emitting element140 determines the light output of the light-emitting element part 140.Especially, if the light-emitting element 140 is the surface emittingsemiconductor laser, the light output of the light-emitting element part140 fluctuates widely depending on surrounding temperature of thelight-emitting element part 140 or a lifespan of the light-emittingelement part 140. Therefore, in the light-emitting element part 140, itis required to maintain the light output at predetermined values asfollows: monitoring the light output of the light-emitting element part140, a voltage applying to the light-emitting element part 140 iscontrolled based on a value of the current produced in thelight-receiving element part 120 so as to adjust a value of the currentflowing in the light-emitting element part 140. As a result, the lightoutput of the light-emitting element part 140 is maintained. Control,where the light output of the light-emitting element part 140 is fedback to the voltage value applying to the light-emitting element part140 can be carried out by using an outer electric circuit (a drivecircuit, not shown).

In this exemplary embodiment, while a case where the electro-opticalelement 100 is the surface emitting semiconductor laser has beendescribed, any electro-optical element, other than the surface emittingsemiconductor laser, is applicable.

As for the electro-optical element that is applicable for the invention,for example, a semiconductor light emitting diode or the like areexemplified. The above will be applied to the electro-optical elementaccording to the second to fourth exemplary embodiment of the inventiondescribed later in the same manner.

2. Operation of the Electro-Optical Element

General operation of the electro-optical element 100 in this embodimentwill be described below. A driving method for the surface emittingsemiconductor laser described below is an example. Various modificationscan be made within the scope of the gist of the invention.

A forward voltage is applied to the pin diode by the first electrode 107and the second electrode 109. A recombination of electron and positivehole occurs in the active layer 103 of the light-emitting element part140, thereby generating light due to the recombination. Then, an inducedemission occurs when the light travels forward and backward from thesecond mirror 104 to the first mirror 102, thereby amplifying anintensity of the light. If an optical gain exceeds an optical loss, alaser oscillates such that laser light emits from the upper surface 104a of the second mirror 104 and is incident on the first contact layer111 of the light-receiving element part 120.

Next, in the light-receiving element part 120, the light that has beenincident on the first contact layer 111 is incident on the lightabsorption layer 112. As the result is that a part of the incident lightis absorbed in the light absorption layer 112, the light excitationoccurs in the light absorption layer 112, thereby producing the electronand positive hole. By the electric field applied from the outside of theelement, the electron is moved to the third electrode 116, and the holeis moved to the fourth electrode 110.

As a result, a current (a light current) arises in a direction from thefirst contact layer 111 to the second contact layer 113 in thelight-receiving element part 120. The light output of the light-emittingelement part 140 can be detected by measuring the value of the current.Also, the light that has passed through the light-receiving element part120 is emitted from the optical member 160, in which a radiation angleof the light is reduced.

3. Method to Manufacture an Exemplary Embodiment of an Electro-OpticalElement

Next, an example of an exemplary method to manufacture theelectro-optical element 100 according to the first exemplary embodimentof the invention will be described with reference to FIGS. 3 through 10.FIGS. 3 through 10 are schematics illustrating one manufacturing processof the electro-optical element in FIG. 1. Each of the schematics iscorresponding to a sectional view in FIG. 1.

(1) First, a semiconductor multilayer film 150 is grown epitaxially on asurface 101 a of the semiconductor substrate 101 including the n-typeGaAs by changing and controlling its composition as shown in FIG. 3.Here, the semiconductor multilayer film 150 is formed of the following:the first mirror 102 including 40 pairs of a n-type Al_(0.9)Ga_(0.1)Aslayer and a n-type Al_(0.15)Ga_(0.85)As layer alternately deposited; theactive layer 103 including a Al_(0.3)Ga_(0.7)As barrier layer and a GaAswell layer that includes a quantum well structure constructing threelayers; the second mirror 104 including 29.5 pairs of a p-typeAl_(0.9)Ga_(0.1)As layer and a p-type Al_(0.15)Ga_(0.85)As layeralternately deposited; the first contact layer 112 including the n-typeGaAs; and the second contact layer 113 including the p-type GaAs.Depositing those layers one after another, the semiconductor multilayerfilm 150 is formed (refer to FIG. 3).

In the growing of the second mirror 104, at least one layer that iscloser to the active layer 103 is formed as an AlAs layer or AlGaAslayer containing 95% or more Al. This layer will be oxidized later so asto be the current constriction layer 105 (refer to FIG. 7). A carrierdensity may be high in the vicinity of a part of the second mirror 104where the second mirror 104 contacts at least the second electrode 109,so as to easily take an ohmic contact-connection to the second electrode109 in a later process in which the second electrode 109 is formed. In asimilar way, that a carrier density may be high in the vicinity of apart of the first contact layer 111 where the first contact layer 111contacts at least the third electrode layer 116 so as to easily take theohmic contact-connection to the third electrode 116.

The temperature for the epitaxial growing is accordingly determineddepending on a method to grow a row material, a type of thesemiconductor substrate 101, a type and thickness of the semiconductormultilayer to be formed, and the carrier density. Generally, 450 degreescentigrade to 800 degrees centigrade is preferred. Also, a processingtime for the epitaxial growing is accordingly determined as the samemanner of the temperature. As for a method for the epitaxial growing, ametal-organic vapor phase epitaxy (MOVPE), a molecular beam epitaxy(MBE), or a liquid phase epitaxy (LPE) can be employed.

(2) Next, the second contact layer 113 and the light absorption layer112 are patterned of a predetermined shape (refer to FIG. 4).

First, a photoresist (not shown) is applied on the semiconductormultilayer film 150. The photoresist is patterned by a photolithographymethod so as to form a resist layer R1 of a predetermined pattern.

Next, the second contact layer 113 and the light absorption layer 112are etched by a dry-etching method, for example, using the resist layerR1 as a mask. Accordingly, the second contact layer 113 and the lightabsorption layer 112 having the same plane shape as that of the secondcontact layer 113 are formed. Then, the resist R1 is removed.

(3) Next, the first contact layer 111 is patterned of a predeterminedshape (refer to FIG. 5). Specifically, at the first, the photoresist(not shown) is applied on the first contact layer 111. The photoresistis patterned by the photolithography method so as to form a resist layerR2 of a predetermined pattern (refer to FIG. 5).

Next, the first contact layer 111 is etched by a dry-etching method, forexample, using the resist layer R2 as a mask. Accordingly, thelight-receiving element part 120 is formed as shown in FIG. 7. Then, theresist R2 is removed. The light-receiving element part 120 includes thesecond contact layer 113, the light absorption 112, and the firstcontact layer 111. A plane shape of the first contact layer 111 can beformed larger than that of the second contact layer 113 and the lightabsorption layer 112.

In above-mentioned processes, the first contact layer 111 is patternedafter the patterning of the second contact layer 113 and the lightabsorption layer 112. Alternatively, the patterning of the secondcontact layer 113 and the light absorption layer 112 may be patternedafter patterning of the first contact layer 111.

(4) Next, the light-emitting element part 140, including the columnarpart 130, is formed by the patterning (refer to FIG. 6). Specifically,first, the photoresist (not shown) is applied on the second mirror 104.The photoresist is patterned by the photolithography method so as toform a resist layer R3 of a predetermined pattern (refer to FIG. 6).

Next, the second mirror 104, the active layer 103, and a part of thefirst mirror 102 are etched by the dry-etching method, for example,using the resist layer R3 as a mask, thereby forming the columnar part130 as shown in FIG. 6. A resonator including the columnar part 130 (thelight-emitting element part 140) is formed by processes as describedabove. Specifically, a stacked body made up of the light-emittingelement part 140 and the light-receiving element part 120 is formed.Then, the resist layer R3 is removed.

As mentioned above, in this exemplary embodiment, the light-receivingelement part 120 has been formed prior to the formation of the columnarpart 130. Alternatively, the light-receiving element part 120 may beformed after the formation of the columnar part 130.

(5) Next, the semiconductor substrate 101 in which the columnar part 130has been formed in processes described above is subjected to, forexample, water vapor at approximately 400 degrees centigrade, so as toform the current constriction layer 105 by oxidizing the layercontaining high composition Al in the second mirror 104 from its side(refer FIG. 7).

An oxidation rate depends on temperature of a furnace, a supply amountof water vapor, Al composition and a thickness of a layer to be oxidized(the layer containing high composition Al described above). In a surfacelight-emitting laser including the current constriction layer formed bythe oxidization, a current flows through only a part where the currentconstriction layer has not been formed (a part where the oxidization hasnot been done) at a time of driving. Therefore, controlling an areawhere the current constriction layer 105 is formed in its formingprocess with the oxidation, a current density can be controlled.

Also, a diameter of the current constriction layer 105 may be adjustedso that a large portion of the light emitted from the light-emittingelement part 140 is incident on the first contact layer 111.

(6) Next, the second electrode 109 is formed on the upper surface 104 aof the second mirror 104. Then, the fourth electrode 110 is formed onthe top of the light-receiving element part 120 (on an upper surface 113a of the second contact layer 113) (refer to FIG. 8).

First, prior to forming the second electrode 109 and the fourthelectrode 110, the upper surface 104 a of the second mirror 104 and theupper surface 113 a of the second contact layer 113 are cleaned by aplasma treatment method or the like, if necessary. This enablesformation of an element having more stable characteristic.

Next, a deposited multiple layer of, for example, Pt, Ti, and Au (notshown) is formed, for example, by a vacuum deposition method. Then, thedeposited multiple layer excluding a predetermined position is removedby a liftoff method so as to form the second electrode 109 and thefourth electrode 110. In this process, a part, to which the depositedmultiple layers described above is not provided, is formed on the uppersurface 113 a of the second contact layer 113. This part forms theopening 114 and its bottom is the optical surface 108. Inabove-mentioned process, the dry-etching method also can be used insteadof the liftoff method. Additionally, while the second electrode 109 andthe fourth electrode 110 are patterned together in above-mentionedprocess, the second electrode 109 and the fourth electrode 110 can bepatterned individually.

(7) Next, in the same manner, patterning the deposited multiple layermade up of, for example, Au and an allay of Au and Ge, the firstelectrode 107 is formed on the first mirror 102 of the light-emittingelement part 140, and the third electrode 116 is formed on the firstcontact layer 111 of the light-receiving element part 120 (refer to FIG.9).

Then, an annealing is done. Temperature of the annealing depends on anelectrode material. As for the electrode material used in this exemplaryembodiment, it is usually done approximately at 400 degrees centigrade.The first electrode 107 and the third electrode 116 are formed byprocesses described above (refer to FIG. 9). The first electrode 107 andthe third electrode 116 can be formed by the patterning at together orindividually.

Processes mentioned above achieve the electro-optical element 100including the light-emitting element part 140 and the light-receivingelement part 120.

(8) Next, the optical member 160 is formed on the light-receivingelement part 120 (refer to FIGS. 9 and 10). In this exemplaryembodiment, a case where a part of the optical member 160 is formed onthe optical surface 108, and another part of the optical member 160 isformed on the light-receiving element part 120 with the fourth electrode110 (refer to FIG. 1) will be described.

First, a treatment to adjust a wet angle of the optical member 160 iscarried out on the upper surface of the light-receiving element part 120(on the surface of the second contact layer 113 and the optical surface108), if necessary. This process makes it possible to achieve an opticalmember precursor 160 b as a predetermined shape if the liquid materialis introduced on the upper surface of the light-receiving element part120 in a process described later, thereby achieving the optical memberhaving a predetermined shape (refer to FIGS. 9 and 10).

Then, a liquid drop 160 a of the liquid material is ejected toward theoptical surface 108 by inkjet method for example. Examples of an inkjetejection method include (1) a method that the size of bubbles in anejection liquid (here, the liquid for optical member precursor) arechanged by heat so as to generate pressure, thereby ejecting the liquid,and (2) a method that pressure generated by piezoelectric elements ejectliquid. From a controllability of pressure point of view, a methoddescribed above in (2) is preferable.

An alignment between a nozzle position of an inkjet head and an ejectingposition of the liquid is carried out by a related art image recognitiontechnique that is used in an exposure process or an inspection processof a general manufacturing process of a semiconductor integratedcircuit. For example, the alignment between a position of a nozzle 170of an inkjet head 180 and a position of an optical surface 108 iscarried out as shown in FIG. 9. After the alignment, the inkjet head 180ejects the liquid drop 160 a of the liquid material by controlling avoltage applied to the inkjet head 180. Accordingly, the optical memberprecursor 160 b is formed on the upper surface of the light-receivingelement part 120 as shown in FIG. 9.

In this case, as shown in FIG. 9, at the time when the liquid drop 160 aejected from the nozzle 170 lands on the upper surface of thelight-receiving element part 120, the liquid material 160 b is deformedby surface tension, thereby positioning the liquid material 160 b at thecenter of the upper surface of the light-receiving element part 120.Accordingly, the position is automatically adjusted.

Also, in this case, the optical member precursor 160 b (refer to FIG.10) has a shape and size in accordance with a shape and size of theupper surface of the light-receiving element part 120, an ejectingamount of the liquid drop 160 a, surface tension of the liquid drop 160a, and surface tension between the upper surface of the light-receivingelement part 120 and the liquid drop 160 a. Therefore, controlling thesefactors, a shape and size of the optical member 160 that is finallyachieved (refer FIG. 1) can be controlled, thereby increasing a freedomof a lens design.

After completion of the processes described above, as shown in FIG. 10,the optical member precursor 160 b is cured by an energy ray (forexample, an ultraviolet ray) so as to form the optical member 160 on theupper surface of the light-receiving element part 120 (refer to FIG. 1).Here, the optimum wavelength and irradiation amount of the ultravioletray depends on a material of the optical member precursor 160 b. Forexample, if a precursor of an acrylic-type ultraviolet curable resin isused to form the optical member precursor 160 b, the curing is done bythe ultraviolet ray irradiation with the condition that the wavelengthis approximately 350 nm, intensity is 100 mw, and irradiation time is 5minutes. The processes mentioned above achieve the electro-opticalelement 100 of the exemplary embodiment as shown in FIG. 1.

4. Beneficial Effects

The electro-optical element 100 of the exemplary embodiment includesbeneficial effects as follows.

(A) First, by providing the optical member 160 at least on the opticalsurface 108, the light generated in the light-emitting element 140 canbe emitted outside after adjusting its radiation angle. For example, byproviding the optical member 160, the radiation angle of the lightgenerated in the light-emitting element 140 can be reduced. Accordingly,if the light emitted from the electro-optical element 100 of theexemplary embodiment is introduced into an optical waveguide, such as anoptical fiber or the like, this makes it easier to introduce the lightto the optical waveguide.

(B) Second, the size and shape of the optical member 160 can be strictlycontrolled. As above-mentioned in the process (8), in order to form theoptical member 160, the optical member precursor 160 b is formed on theupper surface of the light-receiving element part 120 in the process toform the optical member 160 (refer to FIGS. 8 and 9). Here, as long asthe liquid material making the optical member precursor 160 b does notwet a side of the light-receiving element part 120, surface tension ofthe liquid material principally acts on the optical member precursor 160b. Therefore, the shape of the optical member precursor 160 b can becontrolled by controlling an amount of the liquid material (the liquiddrop 160 a) used to form the optical member 160. This makes it possibleto form an optical member 160 whose shape is strictly controlled. As aresult, the optical member 160 having a predetermined shape and size canbe achieved.

(C) Third, a placement position of the optical member 160 can bestrictly controlled. As above-mentioned, the optical member 160 isformed as follows. At first, ejecting the liquid drop 160 a on the uppersurface of the light-receiving element part 120, the optical memberprecursor 160 b is formed. Then, the optical member precursor 160 b iscured (refer to FIGS. 9 and 10). Generally, it is difficult to strictlycontrol the position on which the ejected liquid lands. However, thismethod makes it possible to form the optical member 160 on the uppersurface of the light-receiving element part 120 without positioning.Specifically, simply ejecting the liquid drop 160 a on the upper surfaceof the light-receiving element part 120, the optical member precursor160 b can be formed without positioning. This enables the optical member160, whose placement position is controlled, to form simply and at ahigh yield rate.

If the liquid drop 160 b is ejected by the inkjet method, it can ejectthe liquid drop 160 b to a more accurate position, thereby enabling theoptical member 160, whose placement position is more controlled, to formsimply and at a high yield rate. Also, ejecting the liquid drop 160 a bythe inkjet method, the ejecting amount of the liquid drop 160 b can becontrolled at a unit of a picoliter order, thereby enabling a precisestructure to form accurately.

(D) Fourth, feeding back a result of a part of the output light of thelight-emitting element part 140 monitored in the light-receiving elementpart 120 to the drive circuit, an output fluctuation due to temperatureor the like can be corrected, thereby achieving a stable light output.

Second Exemplary Embodiment

1. Construction of the Electro-Optical Element.

FIG. 11 is a schematic illustrating an electro-optical element 200according to a second exemplary embodiment of the invention. In thisexemplary embodiment, in the same manner as that of the first exemplaryembodiment, a case where the light-emitting element part 240 functionsas a surface emitting semiconductor laser and the light-receivingelement part 220 functions as a light-detecting part is described.

The electro-optical element 200 of the exemplary embodiment differs fromthe electro-optical element 100 of the first exemplary embodiment inthat the light-receiving element part 220 and the light-emitting elementpart 240 are deposited on a semiconductor substrate 201 in this order.As for the electro-optical element 200 of the exemplary embodiment, asimilar construction element to a construction element described as“1XX” in the electro-optical element 100 of the first exemplaryembodiment is described as “2XX”. Therefore, the “2XX” represents thesame construction element and is basically made of the same material asthe “1XX” in the electro-optical element of the first exemplaryembodiment, thereby omitting its detailed description.

The electro-optical element 200 of the exemplary embodiment includes alight-receiving element part 220 formed on the semiconductor substrate201 and a light-emitting element part 240 formed on the light-receivingelement part 220. This electro-optical element 200 can emit light in thedirection that the light-emitting element part 240 and thelight-receiving element part 220 are formed in layers.

The light-receiving element part 220 includes a second contact layer213, a light absorption layer 212, and a first contact layer 211. Thesecond contact layer 213 doped p-type, the light absorption layer 212,and the first contact layer 211 doped n-type are deposited on thesemiconductor substrate 201 made of the p-type GaAs in this order. Thesecond contact layer 213, the light absorption layer 212, and the firstcontact layer 211 can be formed by the same material as that of thesecond contact layer 113, the light absorption layer 112, and the firstcontact layer 111 in the first exemplary embodiment of the inventionrespectively.

The light-emitting element part 240 includes a second mirror 204, anactive layer 203, and a first mirror 202. The second mirror 204 dopedp-type, the active layer 203, and the first mirror layer 202 dopedn-type are deposited on the light-receiving element part 220 in thisorder. The second mirror 204, the active layer 203, and the first mirror202 can be formed from the same material as that of the mirror 104, theactive layer 103, and the first mirror 102 of the first exemplaryembodiment respectively. Also, a current constriction layer 205 isformed to the second mirror 204 the same as that of the second mirror104 of the first exemplary embodiment.

Also, the electro-optical element 200 in the exemplary embodimentincludes a first electrode 207, a second electrode 209, a thirdelectrode 216, and a fourth electrode 210. The first electrode 207 andthe second electrode 209 are used to drive the light-emitting elementpart 240. The third electrode 216 and the fourth electrode 210 are usedto drive the light-receiving element part 220. The first electrode 207is formed on the second mirror 207. The second electrode 209 and thethird electrode 216 are formed on the first contact layer 211. Thefourth electrode 210 is formed on the second contact layer 213. Thesecond electrode 209, the third electrode 216, and the fourth electrode210 have substantially the plan shape of a ring. The second electrode209 is formed so as to surround the light-emitting element part 240 andthe third electrode 216 and the fourth electrode 210 are formed so as tosurround the light-receiving element part 220. Specifically, thelight-emitting element part 240 is formed inside the second electrode209 and the light-receiving element part 220 is formed inside the fourthelectrode 210. Also, the second electrode 209 contacts a side of thesecond mirror 204. A part of the second electrode 209 is formed on thethird electrode 216.

Also, in the electro-optical element 200 of the exemplary embodiment, ifa face of the light-receiving element part 220 contacting a opticalmember 260 is defined as its upper surface, and a face of thelight-receiving element part 20 contacting the light-emitting elementpart 240 is defined as its lower surface, an optical surface 208 isformed on the upper surface of the light-receiving element part 220.Specifically, an opening 214 that passes through the semiconductorsubstrate 201 is provided to the semiconductor substrate 201. A bottomof the opening 214 defines the optical surface 208. The optical member206 is formed on the optical surface 208. The optical member 260 isburied in the opening 214.

As shown in FIG. 11, it enables the longest diameter of thecross-sectional surface, that is obtained by cutting the optical member260 with a plane parallel to the optical surface 208 to be larger thanthe longest diameter of the optical surface 208.

2. Operation of the Electro-Optical Element

In the electro-optical element 200 of the exemplary embodiment, astacking order of the light-receiving element part 240 and thelight-emitting element part 220 is the opposite of that in theelectro-optical element 100 of the first exemplary embodiment. However,a basic operation of the electro-optical element 200 of the exemplaryembodiment is the same as that of the electro-optical element 100 of thefirst exemplary embodiment, thereby omitting its detailed description.

Consequently, in the electro-optical element 200 of the exemplaryembodiment, a part of the light generated in the light-emitting elementpart 240 passes through the light-receiving element part 220 and emitsfrom the optical surface 208. Then, it is emitted to the outside fromthe optical member 260 in which its radiation angle is reduced. The partof the light generated in the light-emitting element part 240 isabsorbed in the optical absorption layer 212 so as to be converted to acurrent. As a result, the light output generated in the light-emittingelement part 240 is detected.

3. Beneficial Effect

The electro-optical element 200 of the exemplary embodimentsubstantively includes the same effect as that of the electro-opticalelement 100 of the first exemplary embodiment. In addition, as for theelectro-optical element 200 of the exemplary embodiment, since theoptical member 260 is provided in the opening 214, the optical member260 can be placed on the optical surface 108 stably.

Also, the optical member 260 is formed by curing the optical memberprecursor (not shown) that has been formed by dropping the liquid dropinto the opening 214. Accordingly, adjusting a shape and a size of theopening 214, the optical member 260 can be made as a predetermined shapeand size.

Third Exemplary Embodiment

1. Construction of the Electro-Optical Element

FIG. 12 is a schematic illustrating an electro-optical element 300according to a third exemplary embodiment of the invention. Also, FIG.13 is a schematic illustrating the electro-optical element 300 shown inFIG. 12. In this exemplary embodiment, in the same manner as that of thefirst exemplary embodiment and the second exemplary embodiment, a casewhere the light-emitting element part 240 functions as a surfaceemitting semiconductor laser and the light-receiving element part 220functions as a light-detecting part is described.

The electro-optical element 300 according to the exemplary embodimentincludes the same construction as that of the electro-optical element100 of the first exemplary embodiment. Therefore, a construction elementthat is substantively the same as that of the electro-optical element100 of the first exemplary embodiment is labeled as the same, therebyomitting its detailed description.

In the electro-optical element 300, the light-receiving element part 120additionally has a function to absorb the light that is incident on theoptical surface 108 after passing through the optical member 160 fromthe outside and convert it to a current. An optical thickness d isrepresented by the following formula (1), where λ is a design wavelengthof the light-emitting element part.d=mλ/2  Formula (1)(m is a natural number greater than or equal to one)

In the electro-optical element 300 of the exemplary embodiment, theoptical thickness d of the light-receiving element part 120 is asummation of the each optical thickness of the first contact layer 111,the light absorption layer 112, and the second contact layer 113 asshown in FIG. 12. Since the optical thickness is a value that iscalculated by multiplying an actual film thickness of the layer by arefractive index, for example, in case of the layer where the opticalthickness is λ/4, the refractive index n is 2.0, and light wavelength isλ, the actual film thickness of the layer is equal to (the opticalthickness)/(the refractive index n). Therefore, (λ/4)/2.0=0.125λ. Inthis exemplary embodiment, “thickness” refers to the actual thickness ofthe layer.

Setting the optical thickness d of the light-receiving element part 120so as to satisfy the formula (1) described above, light of a specifiedwavelength can be absorbed efficiently in the light absorption layer 112of the light-receiving element part 120.

In the electro-optical element 300 of the exemplary embodiment, FIG. 14shows a first rate (reflectance factor) of the light that is incident onthe light-receiving element part 120 from the optical surface 108reflected in the light-receiving element part 120 and a second rate(reflectance factor) of the light that is incident on the second mirror104 from the active layer 103 reflected in the second mirror 104. Thefirst rate, specifically, a reflectance factor of the light that isincident on the light-receiving element part 120 from the opticalsurface 108, is presented by a solid line and the second rate,specifically, a reflectance factor of the light that is incident on thesecond mirror 120 from the active layer 103 is presented by a brokenline respectively in FIG. 14. Here, this case is based on the conditionsas follows. The design. wavelength λ is 850 nm. The optical thickness dof the light-receiving element part 120 is 2λ. The second mirror 104 ofthe light-emitting element part 140 is made up of 29.5 pairs of thep-type Al_(0.9)Ga_(0.1)As layer having the optical thickness of λ/4 andthe p-type Al_(0.15)Ga_(0.85)As layer having the optical thickness ofλ/4 alternately deposited one after another.

Referring to FIG. 14, if the light of the design wavelength λ isincident on the second mirror 104 from the active layer 103, thereflectance factor of the light is nearly 100%. If the light of thedesign wavelength λ is incident on the light-receiving element part 120from the optical surface 108, the reflectance factor of the light isnearly 0%. Therefore, if the light of the design wavelength λ isincident on the light-receiving element part 120 from the opticalsurface 108, most of the light is absorbed in the light-receivingelement part 120.

From the above-mentioned results, according to the electro-opticalelement 300, setting the optical thickness d of the light-receivingelement part 120 so as to satisfy the formula (1), the light can beabsorbed efficiently in the light absorption layer 112 without changingof the construction of the light-emitting element part 140. Therefore,the light that is incident on the optical surface 108 from the outsidecan be introduced efficiently into the optical absorption layer 112 ofthe light-receiving element part 120.

Also, in the electro-optical element 200 of the second exemplaryembodiment, the light-receiving element part may include the functionthat converts the light entered from the outside to the current as inthe same manner as that of the electro-optical element 300 of theexemplary embodiment. In this case, setting the optical thickness of thelight-receiving element part so as to satisfy the formula (1), the sameeffect as that of the electro-optical element 300 of the exemplaryembodiment can be achieved.

2. Operation of the Electro-Optical Element.

In the electro-optical element 300 of the exemplary embodiment, thelight-receiving element part 120 absorbs the light from the outside andconverts it to current as described above. In this case, the light fromthe outside is incident on the optical member 160. Then, the light isincident on the light-receiving element part 120 from the opticalsurface 108. The light is absorbed by the light absorption layer 112 andconverted to the current. With the value of the current obtained there,an amount of the light that is entered from the outside can be detected.The light generated in the light-emitting element part 140 passesthrough the light-receiving element part 120. Then, the light is emittedfrom the optical member 160 in which its radiation angle is reduced.Operations other than those described above are the same as those of theelectro-optical element 100 of the first exemplary embodiment, therebyomitting their detailed descriptions.

3. Beneficial Effect.

The electro-optical element 300 and the method to manufacture thereofaccording to the exemplary embodiment include the beneficial effect thatis substantively the same as that of the electro-optical element 100 andthat of the method to manufacture thereof according to the firstexemplary embodiment.

Additionally, according to the electro-optical element 300 of theexemplary embodiment, the light-receiving element part 120 absorbs thelight from the outside and converts it to current. In this case, sincethe optical member 160 is formed on the optical surface 108, a widerange of light can be incident on the optical surface 108.

The optical member 160 is formed as follows. At the first, ejecting theliquid drop on the upper surface of the light-receiving element part120, the optical member precursor 160 b is formed. Then, the opticalmember precursor 160 b is cured.

Accordingly, as shown in FIGS. 12 and 13, this enables the longestdiameter, specifically diameter r1, of the cross-section of the opticalmember 160, to be larger than the diameter r2 of the upper surface ofthe light-receiving element 120. Thus, this makes it possible toincrease the diameter of the optical member 160, thereby enabling awider range of light to be incident on the optical surface 108.

Also, in the electro-optical element 300 of the exemplary embodiment,the first electrode 107 and second electrode 109 formed in thelight-emitting element part 140 have in plan a substantially ring shape(refer to FIG. 13). If the light-emitting element part 140 functions asthe surface emitting semiconductor laser, since the first electrode 107and second electrode 109 have a substantially ring shape in plan,current can flow uniformly in the light-emitting element part 140.

Each sectional view of the first electrode 107, the second electrode109, the columnar part 130, and the light-receiving element part 120 isplaced to be in a substantially concentric circle. Specifically, thecolumnar part 130 and the second electrode 109 are formed inside thefirst electrode 107 and the light-receiving element part 120 is formedinside the second electrode 109. Therefore, as shown in FIG. 12, theoptical surface 108 formed on the upper surface of the light-receivingelement part 120 is smaller than the cross-sectional surface of thelight-emitting element part 140. As a result, this makes it difficult tointroduce the light from the outside through the optical surface 108.

However, in the electro-optical element 300 of the exemplary embodiment,by providing the optical member 160 on the optical surface 108, thelight from the outside can be introduced efficiently through the opticalsurface 108. Consequently, while the first electrode 107 and secondelectrode 109 have a substantially ring shape in plan, the light can beintroduced efficiently through the optical surface 108.

Fourth Exemplary Embodiment

FIG. 15 is a schematic illustrating an optical module 500 according to afourth exemplary embodiment of the invention. The optical module 500includes the electro-optical element 400 (a first electro-opticalelement 400 a, a second electro-optical element 400 b), a semiconductorchip 20, and an optical waveguide (an optical fiber 30). In theelectro-optical element 400, a light-receiving element part 320 includesa first function of converting the light that is incident on an opticalsurface 308 from a light-emitting element part 340 to current and asecond function of converting the light that is incident on an opticalsurface 308 from an optical member 360 to current in the same manner ofthe electro-optical element 300 of the third exemplary embodiment.Hereafter, a construction or a function that is common between the firstelectro-optical element 400 a and the second electro-optical element 400b is described as “400”.

In the optical module 500 of the exemplary embodiment, even if theelectro-optical element 300 of the third exemplary embodiment isemployed instead of the electro-optical element 400, the beneficialeffect that is the same as that of the electro-optical element 400 canbe achieved. This is applied to a fifth and a sixth exemplary embodimentdescribed later in the same manner.

1. Construction of the Electro-Optical Element

As for the optical module 500, the first electro-optical element 400 aand the second electro-optical element 400 b are provided to an edge 30a and an edge 30 b, respectively, as shown in FIG. 15. The first andsecond electro-optical elements 400 include the same construction aseach other. The first and second electro-optical elements 400 eachinclude the light-emitting element part 340 and the light-receivingelement part 320. Each layer constructing the light-emitting elementpart 340 and the light-receiving element part 320 has nearly the sameconstruction as the light-emitting element part 140 and thelight-receiving element part 120 of the electro-optical element 100shown in FIG. 1 excluding a placement position of the electrode. In FIG.15, a label of each layer constructing the light-emitting element part340 and the light-receiving element part 320 is omitted.

As for the electro-optical element 400 shown in FIG. 15, a firstelectrode 307 and a second electrode 309 function in order to drive thelight-emitting element part 340. The second electrode 309 and the fourthelectrode 310 function in order to drive the light-receiving elementpart 320. Also, an opening 314 is formed at a part of a region of thefourth electrode 310 located on the light-receiving element part 320. Abottom of the opening 314 is an optical surface 308.

In addition, an optical member 360 is formed on the optical surface 308.The optical member 360 is made of the same material of and can be formedin the same manner of the optical member 160 of the electro-opticalelement 100 shown in FIG. 1. As for the first electrode 307 through thefourth electrode 310, a part of each of which is formed on an insulatinglayer 306. The insulating layer 306 may be a resin, such as apolyimide-type resin, a fluorocarbon-type resin, an acrylic-type resin,an epoxy-type resin or the like, or an insulating material, such assilicon nitride, silicon oxide, silicon nitride oxide or the like.

Each of the first electro-optical element 400 a and the secondelectro-optical element 400 b function as a light-receiving element or alight-emitting element respectively. The optical module 500 makesbidirectional communication possible. If the first electro-opticalelement 400 a functions as the light-emitting element and the secondelectro-optical element 400 b functions as the light-receiving element,the light generated in the light-emitting element part 340 of the firstelectro-optical element 400 a emits from the optical surface 308 and isincident on the optical member 360. Then, the light that emits from theoptical member 360 in which the light is condensed and is incident onthe edge 30 a of the optical fiber 30. The incident light transmitsthrough the optical fiber 30 so as to exit from the edge 30 b.Subsequently, the light is incident on the optical surface 308 of thesecond electro-optical element 400 b after passing through the opticalmember 360. Then, the light is absorbed in the light-receiving elementpart 320 of the second electro-optical element 400 b.

Alternatively, if the first electro-optical element 400 a functions asthe light-receiving element and the second electro-optical element 400 bfunctions as the light-emitting element, the light generated in thelight-emitting element part 340 of the first electro-optical element 400b is emitted from the optical surface 308 and is incident on the opticalmember 360. Then, the light is emitted from the optical member 360 inwhich the light is condensed and is incident on the edge 30 b of theoptical fiber 30. The incident light transmits through the optical fiber30 so as to exit from the edge 30 a. Subsequently, the light is incidenton the optical surface 308 of the second electro-optical element 400 aafter passing through the optical member 360. Then, the light isabsorbed in the light-receiving element part 320 of the secondelectro-optical element 400 a.

A relative position of the first electro-optical element 400 a withrespect to the edge 30 a of the optical fiber 30 is fixed. A relativeposition of the first electro-optical element 400 b with respect to theedge 30 b of the optical fiber 30 is fixed. The optical surface 308 ofthe first electro-optical element 400 a faces the edge 30 a of theoptical fiber 30. The optical surface 308 of the first electro-opticalelement 400 b faces the edge 30 b of the optical fiber 30.

The semiconductor chip 20 is provided in order to drive theelectro-optical element 400. Specifically, the semiconductor chip 20includes a circuit in order to drive the electro-optical element 400.Each wiring pattern 24, 34, 64, that is electrically connected to aninner circuit, is provided in multiple numbers on the semiconductor chip20.

The semiconductor chip 20 and the electro-optical element 400 areelectrically connected. For example, the first electrode 307 and thewiring pattern 24 are electrically connected with a solder 26. Also, thesecond electrode 309 and the wiring pattern 64 are electricallyconnected with the solder 26. Additionally, the fourth electrode 310 andthe wiring pattern 34 are electrically connected with the solder 26.

In the electro-optical element 400, the semiconductor chip 20 can beface-down mounted.

Accordingly, the solder allows the electro-optical element 400 and thesemiconductor chip 20 not only to connect electrically but also to fixeach other. As for the connection between each electrode described aboveand the wiring pattern, a wire or a conductive adhesive may be usedinstead of using the solder 26.

An interstice between the electro-optical element 400 and thesemiconductor chip 20 can be fixed by using a resin 56 as shown in FIG.15. Thus, the resin 56 has a function that keeps a connecting conditionbetween the electro-optical element 400 and the semiconductor chip 20.In this case, preventing the optical member 360 from covering the resin56, a refractive index difference between the optical member 311 and itssurrounding can be maintained, thereby ensuring a light condensingfunction of the optical member 360.

A hole 28 (for example, a through hole) is provided to the semiconductorchip 20. The optical fiber 30 is inserted into the hole 28. The hole 28goes through the semiconductor chip 20 from the surface on which theeach wiring pattern 24, 34, 64 is provided to its opposite surface whileavoiding the inner circuit. A taper (not shown) may be provided to atleast one of an opening edge of the hole. By providing the taper, theoptical fiber can be inserted easily into the hole 28.

2. Method to Drive the Optical Module

The method to drive the optical module 500 shown in FIG. 15 will bedescribed with reference to FIG. 16. FIG. 16 is a diagram schematicallyillustrating an example of a drive circuit (a principal part) forelectro-optical element 400 shown in FIG. 15.

In the optical module 500 shown in FIG. 15, control is carried out so asto interchange a light-transmitting and a light-receiving bytime-sharing. As mentioned above, if the first electro-optical element400 a functions as the light-emitting element, the control is carriedout such that the second electro-optical element 400 b receives thelight generated in the first light-emitting element 400 a. If the secondelectro-optical element 400 b functions as the light-emitting element,the control is carried out such that the first electro-optical element400 a receives the light generated in the second light-emitting element400 b. The time-sharing is controlled by a clock 54 and a clock 55 thatare input into a driver IC 40 and a switching circuit 42 respectively.

The drive circuit for the electro-optical element 400 includes thedriver IC 40, the switching circuit 42, and a trans-impedance amplifier(TIA) 44 as shown in FIG. 16. The drive circuit shown in FIG. 16 isprovided for every electro-optical element 400. Additionally, in theelectro-optical element 400, a bias can be applied for thelight-emitting element part 340 and the light-receiving element part 320in the same direction.

The driver IC is electrically connected to one electrode of thelight-emitting element part 340 of the electro-optical element 400. Theswitching circuit 42 is electrically connected to one electrode of thelight-receiving element part 320 of the electro-optical element 400.Another electrode of the light-emitting element part 340 and anotherelectrode of the light-receiving element 320 are grounded as shown inFIG. 16. In addition, a reverse bias is applied to the one electrode ofthe light-receiving element part 320. The TIA 44 is electricallyconnected to the switching circuit 42.

The driver IC 40 is provided in order to drive the light-emittingelement part 340 of the electro-optical element 400. Specifically, thelight generated in the light-emitting element part 340 is emitted whilea transmitting signal 58 is input into the driver IC 40. Also, thelight-receiving element part 320 can monitor an output of the lightgenerated in the light-emitting element part 340 while thelight-emitting element part 340 is operating. Referring to FIG. 16, amovement of the circuit under the operation of the light-emittingelement part 340 will be more specifically described below.

If the transmitting signal 58 is input into the driver IC 40, the driverIC 40 starts to drive the light-emitting element part 340. While thetransmitting signal 58 is input into the driver IC 40, the output of thelight generated in the light-emitting element part 340 is detected bythe light-receiving element part 320. The output of the light detectedis input into the driver IC 40 as an APC input 52 by the switchingcircuit 42.

While the transmitting signal 58 is not input into the driver IC 40, thelight exited from the edge 30 a of the optical fiber 30 is incident onthe optical surface 108 of the electro-optical element 400 after passingthrough the optical member 160. Specifically, while the transmittingsignal 58 is not input into the electro-optical element 400, theswitching circuit 42 is switched to the TIA 44 side (refer to FIG. 16).The TIA 44 has a function of amplifying the receiving signal 50.

As mentioned above, in the optical module 500 of the exemplaryembodiment, the first electro-optical element 400 a and secondelectro-optical element 400 b can be controlled by time-sharing suchthat if the first electro-optical element 400 a is under alight-emitting state, the second electro-optical element 400 b becomes alight-receiving state, and if the first electro-optical element 400 a isunder a light-receiving state, the second electro-optical element 400 bbecomes a light-emitting state.

Fifth Exemplary Embodiment

FIG. 17 is a schematic illustrating an optical transmitting deviceaccording to a fifth exemplary embodiment of the invention. An opticaltransmitting device 90 interconnects electronic equipment 92, such as acomputer, a display, a storage device, a printer or the like. Theelectronic equipment 92 may be information-communication equipment. Theoptical transmitting device 90 may include a plug 96 provided at bothend of a cable 94. The cable 94 includes the optical fiber 30 (refer toFIG. 15). The plug 96 includes the electro-optical element 400 (400 a,400 b) and the semiconductor chip 20. The optical fiber 30 is includedin the cable 94. The electro-optical element 400 and the semiconductorchip 20 are included in the plug 96. Therefore, those are not shown inFIG. 17. A fixing condition between the optical fiber and theelectro-optical element 400 is the same manner as described in thefourth exemplary embodiment.

The electro-optical element 400 a and 400 b of the fourth exemplaryembodiment are provided to both end parts of the optical fiber 30respectively. If the electro-optical element 400 a provided to one endof the optical fiber 30 functions as the light-receiving element, afterconverting a light signal to an electrical signal in the light-receivingelement part 120 of the electro-optical element 400 a, the electricalsignal is input into the electronic equipment 92. In this case, theelectro-optical element 400 b, provided to another end part of theoptical fiber 30, functions as the light-emitting element. Thus, theelectrical signal output from the electronic equipment 92 is convertedto the optical signal in the light-emitting element part 140 of theelectro-optical element 400 b. The optical signal transmits through theoptical fiber 30, inputting into the electro-optical element 400 afunctioning as the light-receiving element.

As above-mentioned, according to the optical transmitting device 90 ofthe exemplary embodiment, communication among the electronic equipment92 can be achieved by the light signal.

Sixth Exemplary Embodiment

FIG. 18 is a schematic illustrating a usage of an optical transmittingdevice according to a sixth exemplary embodiment of the invention. Theoptical transmitting device 90 is connected among electronic equipment80. As for the electronic equipment, a liquid crystal display monitor ora digital CRT (may be used in field of financial, mail-order, medicalcare, education), a liquid crystal projector, a plasma display (PDP), adigital TV, a cash register for retail sales (for point of salesscanning (POS)), a video recorder, a tuner, a game device, a printer orthe like are exemplified.

The present invention is not limited to the above-mentioned exemplaryembodiments. Various changes can be made.

For example, the present invention may include constructions that aresubstantively same as those described in the exemplary embodiments (forexample, the construction including the same functions, method, andresults, or the constructions including the same aims and results).Also, the present invention may include the constructions wherenon-essential parts of the construction described in the exemplaryembodiments are replaced. Also, the present invention may include theconstructions achieving the beneficial effects or constructions that arecapable of achieving the same aims as those of the constructionsdescribed in the exemplary embodiments. Also, the present invention mayinclude constructions adding related arts on the constructions describedin the exemplary embodiments.

For example, in the electro-optical element of the above-mentionedexemplary embodiment, while a case where the light-emitting element partincludes one columnar part has been described, even if the columnar partis provided in multiple numbers in the light-emitting element part, itdoes not adversely affect the exemplary embodiments of the invention.Also, if the electro-optical element is provided in multiple numbers inan array, it includes the same effect.

In addition, in the above-mentioned exemplary embodiment, if the p-typeand n-type are interchanged in the each semiconductor layer, it does notdepart from spirit of the invention. In the above-mentioned exemplaryembodiment, while a case of the AlGaAs has been described, in accordancewith a oscillation wavelength, another material system, for example, asemiconductor material such as a GaInP (gallium-indium-phosphide)system, a ZnSSe (zic-sulfur-selenide) system, an InGaN(indium-gallium-nitride) system, an AlGaN (aluminum-gallium-nitride)system, an InGaAs (indium-gallium-arsenide) system, a GaInAs(gallium-indium-arsenide) system, a GaAsSb (gallium-arsenide-antimony)system are applicable.

1. An electro-optical element, comprising: a light-emitting elementpart; and a light-receiving element part; wherein: an optical thicknessd of the light-receiving element part satisfies the following condition(1):d=mλ/2  (1) where: λ is a design wavelength of the light-emittingelement part, and m is a natural number greater than or equal to one. 2.The electro-optical element according to claim 1, wherein at least anupper part of the light-receiving element part being in a columnar likeshape.
 3. The electro-optical element according to claim 1, thelight-receiving element part including a function of converting a partof the light emitted from the light-emitting element part into acurrent.
 4. The electro-optical element according to claim 1, thelight-receiving element part including a function of converting lightthat is incident on the optical surface from the optical member intocurrent.
 5. The electro-optical element according to claim 1, wherein:the light-emitting element part including a first mirror, an activelayer provided on the first mirror, and a second mirror provided on theactive layer; and the light-receiving element part including a firstcontact layer, a light absorption layer provided on the first contactlayer, and a second contact layer provided on the light absorptionlayer.
 6. The electro-optical element according to claim 1, thelight-emitting element part functioning as a surface emittingsemiconductor laser.
 7. The electro-optical element according to claim1, further comprising an optical member provided at least on an opticalsurface of the light-receiving element part, wherein: a cross-sectionalsurface of the optical member cut by a plane parallel to the opticalsurface being at least one of a circle and an oval; and at least theupper part of the light-emitting element part has a columnar like shape.8. The electro-optical element according to claim 7, wherein a longestdiameter of the cross-sectional surface of the optical member beinglarger than a longest diameter of an upper surface of thelight-receiving element part.
 9. The electro-optical element accordingto claim 7, the optical surface being at least one of a circle and theoval and a longest diameter of the cross-sectional surface of theoptical member being larger than a longest diameter of the opticalsurface.
 10. The electro-optical element according to claim 7, theoptical member being formed by curing a liquid member that is cured byapplying an energy.
 11. The electro-optical element according to claim7, the optical member being formed by an acrylic-type ultravioletcurable resin and epoxy-type resin.
 12. The electro-optical elementaccording to claim 7, the optical member being formed by at least one ofan acrylic-type ultraviolet curable resin, or an epoxy-type resin, and athermosetting polyimide-type resin.
 13. The electro-optical elementaccording to claim 7, the optical member functioning as a lens.
 14. Anelectro-optical element, comprising: a light-emitting element part; anda light-receiving element part having a first contact layer, a lightabsorption layer provided on the first contact layer, and a secondcontact layer provided on the light absorption layer; wherein: a sum dof an optical thickness of the first contact layer, an optical thicknessof the light absorption layer, and an optical thickness of the secondcontact layer satisfies the following condition (1):d=mλ/2  (1) where: λ is a design wavelength of the light-emittingelement part, and m is a natural number greater than or equal to one.